1. Field of the Invention
The present invention relates to a self-traveling machine, and more particularly to a self-traveling machine such as a self traveling robot used for automation of a maintenance service in various plants and factories, and adapted for traveling on a flat or rough surface, ascending and/or descending along a stairway and striding over an obstacle such as piping.
2. Description of the Prior Art
One known self-traveling machine is schematically shown in FIG. 1, in which the machine is ascending or descending on a stairway. This prior machine comprises a body designated at numeral 1, and a pair of drive mechanisms (only one shown) each having an endless belt 7 and a drive sprocket 8 on which the endless belt is entrained. The endless belt 7 is driven by the rotation of the drive sprocket 8 for traveling on a flat or rough surface and along the stairway. The machine has a difficulty in changing the traveling direction because of its construction of the drive mechanism described hereinabove, and also has a drawback in that there is a strong possibility that the machine will damage an obstacle on the ground, such as piping, when the machine rides over it.
There is known another self-traveling machine having four drive mechanisms, each having a crawler unit as shown in FIG. 2 (only one shown in cross section). In FIG. 2, a housing designated at numeral 11 has a bracket 12 disposed therein. The drive mechanism includes a drive shaft 13 rotatably mounted in the bracket 12 at one end and carrying a drive sprocket 21 at the other end, a worm wheel 14 mounted on the shaft 13 coaxially with the sprocket 21, and a cylindrical worm gear 15 operatively coupled with the worm wheel 14. The crawler unit 16 includes a horizontal hollow sleeve 16a and a pivotally movable crawler arm 16b integrally extending perpendicularly from one end of the sleeve 16a. The hollow sleeve is rotatably received in an aperture in the housing 11, and the drive shaft 13 is rotatably received therein. A worm wheel 17 is mounted on the hollow sleeve 16a and is operatively coupled with a cylindrical worm gear 18 which rotates the worm wheel 17 to turn the sleeve 16a and hence the crawler arm 16b. The crawler arm 16b has at its distal end a support rod 19 on which an idler sprocket 20 is freely rotatably mounted. An endless belt 22 is entrained on the drive sprocket 21 and the idler sprocket 20. The drive mechanism in FIG. 2 is in a vertical position in which the lowermost end of the endless belt 22 is in contact with the ground surface G.
For traveling on a flat surface, the worm gear 18 is actuated by an actuator such as a motor (not shown) to rotate the worm wheel to thereby angularly move the crawler arm 16 and hence the idler sprocket 20 downwardly from its uppermost position as shown in FIG. 2 to a position in which a lowermost portion of the idler sprocket 20 is placed on the ground G. Then the worm gear 15 is actuated by the motor to rotate the worm wheel 14 and the drive shaft 13 for thereby rotating the drive sprocket 21 so as to move the endless belt to travel the machine.
To travel along the stairway or stride over the obstacle on the ground the crawler arm is controlled to change its angle into a suitable position and then the worm gear 15 is actuated to rotate the sprocket 21 through the worm wheel 14 and the drive shaft 13 for thereby moving the endless belt to ascend or descend the stairway or stride over the obstacle.
The prior self-traveling machine of the above-described type has a drawback in that the lowermost portion of the housing 11 is disposed insufficiently spaced apart, namely by a distance l, from the surface of the ground, and thus the lowermost part is likely to be interfered with by the rough conditioned surface of the ground, steps of the stairway or the top of the obstacle on the ground. As a result the machine is prevented from traveling any further. This is due to the construction of a power transmission assembly which occupies a relatively large space in a vertical direction about the axis of the drive shaft 13, and more specifically due to the structural arrangement in which the worm wheels 14, 17 are disposed in a vertical position adapted to be directly attached to the horizontal drive shaft 13 and the horizontal hollow sleeve 16a of the crawler arm 16, respectively, and the housing is vertically disposed to enclose all those parts.
The prior machine further has a difficulty in achieving an accurate steering of all the four drive mechanisms which are rotated at speeds different from one another when changing the traveling direction, resulting in that the controlling of the machine becomes tedious.